Filament failure device for electronic tubes



Nov. 20, 1951 1.. L. HELTERLINE, JR., ETAL 2,576 014 FILAMENT FAILURE DEVICE FOR ELECTRONIC TUBES Original Filed Feb. 7, 1948 2 SHEETSSPEET l LED L.HELTERLINE,

MAHE'ELL U5 BEST, JR. AND .ADULPH BUNBLAS ATTORNEY INVEN TORSY.

Nov. 20, 1951 L. L. HELTERLINE, JR., ET AL 2,576,014

FILAMENT FAILURE DEVICE FOR ELECTRONIC TUBES Original Filed Feb. 7, 1948 2 SHEETS-SHEET 2 INVENTORS. LED L. HEL TERLIHE, IVIAREELL U5 BEST, JR. AND Arr DLPH E2 UNBLA SKY BY g as; g

TTORNEY Patented Nov. 20, 1951 FILAMENT FAILURE DEVICE FOR ELECTRONIC TUBES Leo L. Helterline, Jr., South Norwalk, Marcellus Best, Jr., Stamford, and Adolph Bunblasky, New Canaan, Conn., assignors to Sorensen & Company, Inc., Stamford, Conn., a corporation of Connecticut Original application February 7, 1948, Serial No. 6,866. Divided and this application April 1, 1949, Serial No. 84,806

6 Claims.

This invention relates to new and useful improvements in electronic tubes and has particular relation to a filament failure device for electronic tubes.

An object of the invention is to provide an electronic tube having incorporated therein a filament failure feature of commercial value inasmuch as the cost of incorporating the feature in the tube is not excessive.

Other objects and advantages of the invention will become apparent from a consideration of the following detailed description taken in connection with the accompanying drawings wherein a satisfactory embodiment of the invention is shown. However, it is to be understood that the invention is not limited to the details disclosed but includes all such variations and modifications as fall within the spirit of the invention and the scope of the appended claims.

In the drawings:

Fig. 1 is a side elevational view showing a diode tube constructed in accordance with the invention;

Fig. 2 is an enlarged top plan view of the base and elements of said tube, the envelope being omitted and the parts being in normal condition;

Fig. 3 is a side elevational view of the tube parts shown in Fig. 2, the view being as seen from the lower side of Fig. 2;

Fig. 4 is a side elevational view of the device of Fig. 3, the view being as seen from the right of Fig. 3;

Fig. 5 is a view similar to Fig. 2 but showing the relative positions of the parts following filament failure or breakage;

Fig. 6 is an elevational view taken as looking toward the lower side of Fig. 5;

Fig. 7 is a schematic view showing the connections of the tube parts; and

Fig. 8 is a schematic wiring diagram Showing the tube of the invention as employed in the circuit of an electronic voltage regulator.

This application is a division of our application Serial Number 6,866 filed February 7, 1948.

The present invention relates particularly to the above mentioned electronic tube which may be used in a voltage regulator such as that disclosed in application Serial Number 662,751 filed April 1'7, 1946 (now Patent No. 2,455,143 of November 30, 1948) or that disclosed in application Serial Number 740,953 filed April 11, 1947, which has matured as Patent No. 2,569,500 on October 2, 1951, both by Edward M. Sorensen. In Fig. 8 of the present application there is shown an improved voltage regulator resulting from the substitution of the present tube for that disclosed at 13 in Fig. 3 of the above mentioned Sorensen application, Serial Number 740,- 953. However, the invention also contemplates other uses of said tube and specifically contemplates substitution of the present tube having incorporated therein the filament failure feature for the tube 13 of the voltage regulator disclosed in the above identified Sorensen patent.

Referring in detail to the drawings and at first more particularly to Figs. l-7, there is shown the arrangement of the elements in my improved diode tube 10. Said tube comprises an evacuated insulating envelope ll attached to an insulating base l2 provided with prongs or terminals 13 for engaging suitable electrical contacts in a standard tube socket. The insulating envelope II includes a bottom wall portion 14 separated from the base 12. This bottom wall portion securely mounts terminal leads I5, l6, I1 and IB passing therethrough and each in electrical contact with a separate prong I3.

Terminal lead 15 has a right angle bend providing an arm I9 mounting a cylindrical plate electrode 20 welded or otherwise secured thereto. It will be noted that the arm i9 is in tangential contact with plate 20 and said contact is intermediate the ends of said plate. Terminal lead 16 mounts a right angle extension piece 2!, the

horizontal arm of which is rigidly secured to the lead l6 while the other arm of piece 2| inclines laterally and upwardly of said lead. It will be readily seen that a filament 22 is passed longitudinally and co-axially through the cylindrical plate 20 and said filament is welded or otherwise secured at one of its ends to the laterally and upwardly inclined arm of the rigid extension piece 2| as at 23..

Terminal lead ll mounts an extension piece 24 at right angles thereto, one end of said extension piece being rigidly welded or otherwise secured to said lead near one end thereof as at 25. The end of a resilient cantilever spring wire 26 having a slight bend 21 intermediate its end portions is welded or otherwise secured at one end, as at 28, to the rigid arm or extension 24. The spring wire 26 is physically or mechanically forced over or urged into a straightened position against the spring biasing action characteristic of said bend 21 and the force used is of a magnitude so as not to overstress the bend 21 of the spring in any such manner as to prevent its returning to its normal position as shown. in Figs. 5 and 6. 1

With the spring 26 loaded to bring it into the right angle bend forming a pair of legs.

loaded and holds said spring in the described straightened position against its natural biasing action. Furthermore, it is seen that the elements I6, 2|, 22, 26, 24 and I1 are electrically connected in series forming the filament circuit of the tube l0.

Terminal lead 18 mounts a wire 30 having a The function of this wire will later be described. The end of the shorter leg of wire 30 is Welded in an intermediate position on lead I8 and another loop of wire, generally indicated at 3|, is welded near the extreme upper end of the lead [6. This loop 3| comprises a getter assembly.

Referring now to Fig. 8, there is shown therein a bridge circuit comprising three resistors 33, 34 and 35 and the tungsten filament diode ID. This diode with its network (in the present instance comprising the resistances 33, 34 and 35) is the primary control unit of the voltage regulator. The input of the bridge circuit is derived from the secondary 36 of a transformer 31, the primary 38 of which is connected across the A. C. input line 39 and 40, the primary being in series with a winding of an autotransformer as will presently appear.

The transformer secondary 36 is connected to a rectifier tube 4| and the D. C. output of this tube is in turn connected to the input terminals 42 and 43 of the bridge 33, 34, 35 and I0, previously described. Connected across the diagonals 44 and 45 of the bridge circuit is the input circuit of an amplifier tube 46. Tube 46 is supplied with filament current by means of a secondary winding 41 of a power transformer 48, the primary 49 of which is connected directly across the line 39-40. Plate current is supplied to tube 46 from a secondary 50 of the power transformer 48 through a fullwave rectifier and thence over conductors 52, 53, 54, 55, the saturating winding 56 of a saturable core reactor 51 and a conductor 58 to the plate of the tube 46.

Saturable core reactor 51 is provided with an alternating current winding 59, which winding is in series with a portion 60 of the winding of an autotransformer 6|, the other portion 62 of the winding of said autotransformer 6| being in series with the primary 38 of the transformer 31 as previously mentioned. Transformer 31 is also provided with a secondary 63 which secondary is connected by means of conductors 64 and 65 to the input of a bridge type rectifier composed of four selenium rectifiers 66, 61, 68 and 69. The output of the rectifier is in turn connected by means of conductors and 1| to the output terminals 12 and 13. It will be noted that conductor 10 does not lead directly to terminal 12 but instead passes through a portion of a choke coil 14 which serves to filter out any ripple which might be present in the output. A condenser is connected across the output terminals to accentuate the filtering action.

The filament of tube I6 is in electrical connection through spring 26, elements 24 and I1, and conductor 16 to positive polarity of the D. C. output and the other end of the filament connects through elements 2| and I6 and a conductor 11, a variable resistance 18, conductors 19 and 80, a variable resistance 8|, and a conductor 4 82 to terminal 13. In other words, the filament of the diode I0 is connected across the D. C. output and the temperature of said filament is varied in accordance with variations in said output.

The conductor or lead 16 instead of being connected to the conductor 10 at the place shown may be connected to said conductor at a point between the connections of condenser 15 and a condenser 83 with said conductor. This connection is sometimes advantageous since it utilizes the resistance of a coil 14 to vary the character of the load compensation.

From the above it will be seen that the basic power circuit comprises the autotransformer 6| and the saturable core reactor 51, this reactor being in series with the primary of the autotransformer. The portion 62 of the autotransfor'mer 6! is connected in series with the primary winding 38 of transformer 31. Consequently, variation of the impedance of the saturable core reactor 51 will vary the voltage impressed on the primary 60 of the autotransformer 6| and will thereby vary the voltage supplied to the rectifier transformer 31. Thus, a decrease in reactor impedance will increase the portion of the input voltage which is impressed on the autotransformer primary 60 and will result in an increase in output voltage across output terminals 12 and 13. Conversely, an increase in the impedance of reactor 51 will result in a decrease .in the output voltage across terminals 12, 13.

To provide means for varying the reactor impedance by the proper amount to restore the output voltage to its original values at such times as it may vary due to changes in load or input voltage, the electronic control circuit heretofore described is provided. Thus, any change in output voltage across terminals 12, 13 will result in a change in temperature of the filament of diode 10 which results in a change in the cathode emission of this tube and a relatively great change in the plate resistance of the tube. The signal voltage taken oil across the diagonals 44, 45 of the bridge is applied to the beam power tube 46,

. the output of which is in turn fed over a circuit heretofore described to the primary winding 56 of the saturable reactor 51.

In order to make the operation clear it will be assumed that a rise in output voltage has occurred due to a reduction of the load or a rise in input voltage or both. This increased output voltage across terminals 12, 13 results in the application of a greater voltage to the diode filament and additional heating of that filament. With increased heating the cathode of the diode I0 produces increased emission and thus reduces the plate resistance of the tube. Since diode [0 forms an arm of a bridge circuit, as previously described, a change in its plate resistance will change the balance condition of the bridge resulting, in the present instance, in the application of a more positive potential to the control grid of the beam power tube 46.

This positive grid signal results in a sharp increase in the plate current of the tube 46 and consequently produces an increased saturation of the saturable core reactor 51. This increased D. C. saturation of the reactor 51 results in an increase in A. C. impedance and in turn results in lowering of the voltage in the primary 38 of the transformer 31. This in turn results in a reduced voltage applied across the rectifier unit and consequently reduced output voltage across terminals 12, 13. Should the filament of diode I0 break or burn out, a similar action of the circuit scribed immediately above will continue until an equilibrium point is attained, i. e., until the net change in output voltage is suflicient to compensate for the changed conditions in the control circuit. The gain of the control system is of such magnitude that the direct current output voltage will be maintained constant within a tolerance of plus or minus 0.5%.

Tube.4| has already been described as a rectifier in the D. C. power supply for the bridge circuit diode HI. This rectifier tube 4| is supplied with filament heating current by means of a secondary 84 of the transformer 48. Tube 5| has been described as supplying plate currents to the tube 46 and, of course, supplying current to the saturable core reactor winding 56. This tube 5| is supplied with filament heating current by means of a secondary winding 85 of the transformer 48.

A variable resistance 8| is supplied in the circuit to the diode filament, adjustment of this resistance serving to adjust the output voltage to any desired point within the range of operation of the regulator. In order to compensate for variations in the input voltage a potentiometer 18 is supplied, this potentiometer serving to adjust the bias on tube 46 and thereby compensate for variations in the voltage input.

A variable resistance 68a issupplied in the output of the rectifier in order to permit compensation for load variation. It will be clear that as the load increases the drop through resistor 68awill likewise increase and thus the current fiowing in the filament circuit of the diode ID will be proportionally varied and the resistance of the cathode anode circuit of the diode will then compensate for the load change.

As will be obvious, the variation of the resistance in the filament circuit of the diode l varies the value of the output voltage necessary to obtain a given diode filament temperature and will thus control the output voltage. A resistor 86 is connected between the plate and screen of the beam power tube 46, this resistor serving as a swamping resistor to absorb conductive surges which originate in the winding 58 of the saturable core reactor '1. This is necessary because of the very high inductance of this winding.

5 Inserted in the line or conductor 54 is a resistance 88 while 'a resistance 81 is inserted between such line or conductor and the line or conductor 54 and the lines or conductors l9 and 80. Located in the line from the Winding 36 of transformer 31 is a resistance 89, the same being in series with a condenser 8|. Another condenser 80 is located in the lead of the plate of tube 4| while a condenser 52 is connected across the tube 5| and yet another condenser 83 is connected across the outputs I0 and 1|.

The particularvoltage regulator which is shown in Fig. 8 was designed to provide an output voltage of 12 volts D. C. when operatedfrom a supply is replaced. 5

ation of 15% and operating at a-freq'uency of from 50 to 60 cycles per second. The output voltage was adjustable from 11 to 13 volts, the output load being from 5 to 8.5 amperes. It was found that the output voltage could be held to within plus or minus 1% of the preset desired D. C. output. The values 'of the various circuit elements were as follows:

Resistance 33, 34 and 35 1.9 megohms' Resistance 81 10,000 ohms Resistance 88 25,000 ohms Resistance 88 100,000 ohms Resistance 18 15 ohms variable Potentiometer 8| 20 ohms Resistance 88 47,000 ohms Condenser 90 1 6 microfarad Condenser 8|. microfarad Condenser 92.. 4 microfarads Condenser 93 8,000 microfarads Condenser l5 8,000 microfarads Condenser 83 microfarads In the specific unit above mentioned, the vacuum tube In is of the type known as the 2AS15, a temperature limited diode having a spring loaded tungsten filament made by Sorensen 8: Company, Inc., of Stamford, Connecticut. The remaining three tubes are standard tubes, tube 4| being a 2X2 tube, tube 5| a 5Y3 tube, and tube 48 being a 6L6 beam power tube. These three tube types are manufactured by the Radio Corporation of America and others under these designations.

The tube III with filament intact as used in an operable circuit is best shown in Figs. 2, 3 and 4 and in diagram in Fig. 8. Said filament is connected in closed circuit across the output of conductors 10 and 13 as shown in Fig. 8 thereby effecting the electronic emission of the filament to plate due to voltage fluctuations in the output leads. It will be noted that the conductor 12 of positive polarity is electrically connected to the filament 22. Another electrical connection 32 outside the tube connects the plate 20 to the terminal lead I 8 thence to the right angle element 30. It is here noted that element 38. and the spring 26 are in spaced relation and therefore in open circuit with respect to each other as can be seen in Figs. 2, 3 and 7.

Should the filament break or burn out in a tube I0 not provided with a spring loaded filament, the grid of power tube 46 becomes highly negative thereby causing an over-voltage -40% above normal in the D. C. output. This condition is overcome when the spring loaded filament of tube l0 burns out. The biasing action of the spring 28 moves its upper end over to the left bringing it into electrical contact with the outer leg of the bent wire 30 thereby closing a circuit from conductor 16 through elements I1, 24, 28, 30, I8 and lead 32 to the plate 20 and shunting to the grid of tube 46 a positive voltage for reducing the D. C. output voltage. This prevents damage to any instruments in the output circuit. More specifically, the failure of the filament in diode |0 results in such diode becoming a short circuit rather than an open circuit insofar as the bridge or balancing circuit is concerned.

Having thus set forth the nature of our invenof 115 volts single phase A. C. and to saturate the tiOn. What W Claim i saturable coil reactor 51 when the filament of diode I0 is broken or burned out as before described to suppress the high over voltage of the output that would follow. The unit was operable on a supply voltage having a maximum vari- 1. An electronic tube comprising an evacuated envelope and a filament and plate in said envelope, and means within said envelope and movable therein on failure of said filament to short circuit said filament and plate.

means comprising a spring loaded wire connected with said filament. 3. An electronic tube comprising an evacuate envelope and a filament and plate in said envelope, means for short circuiting said filament and plate on failure of said filament, and said means including a spring loaded conductor connected to and anchoring one end of said filament. 4. An electronic tube comprising an evacuated envelope, 2. lead within said envelope, a plate supported within said envelope by said lead, a pair of leads within said envelope, a filament within said envelope and supported at its respective ends by the respective leads of said pair, a fourth lead within said envelope and electrically connected with the first mentioned lead, and means within said envelope under control of said filament and shiftable within said envelope on failure of said filament to move and electrically connect one of the leads of said pair with said fourth lead.

5. An electronic tube comprising a lead. a plate supported by said lead, a pair of leads, a filament supported at its respective ends by the respectiv leads of said pair, a fourth lead electrically connected with the first mentioned lead, means for electrically connecting one of the leads of said pair with said fourth lead on failure of said filament, and said means including a biased spring means normally held in open circuit relation with said fourth lead by said filament.

6. An electronic tube comprising a base, an evacuated envelope on said base, a filament within said envelope, and a plate within said envelope, movable means within said envelope, and said means under control of said filament and being movable in said envelope on failure of said filafient to short circuit said filament and said pla LEO L. HELTERLINE, JR.

MARCELLUS BEST, JR. ADOLPH BUNBLASKY.

REFERENCES CITED The following references are of record in the file of this patent:

FOREIGN PATENTS Number 

